Material conditioners have long been used in processing strip material used in connection with mass production or manufacturing systems. In a manufacturing system, a strip material (e.g., a metal) is typically removed from a coiled quantity of the strip material. However, a strip material may have certain undesirable characteristics such as, for example, coil set, crossbow, edgewave and centerbuckle, etc. due to shape defects and internal residual stresses resulting from the manufacturing process of the strip material and/or storing the strip material in a coiled configuration. A strip material is manufactured using rolling mills that flatten material slabs into the strip material by passing it through a series of rollers. Once flattened, the strip material is typically rolled into a coil for easier handling. Shape defects and internal residual stresses are developed within the strip material as it passes through the rolling mill as it is subjected to non-uniform forces applied across its width.
Laser and/or plasma cutters are often used to cut strip material and perform best when cutting high-quality, substantially flat materials. Internal residual stresses can cause twist or bow in a strip material that can be particularly damaging to laser cutters and/or plasma cutters used to cut the strip material. For example, when the cutting head of a laser cutter and/or a plasma cutter is brought in close proximity to the surface of the strip material, any non-flat portions of the strip material can potentially strike and damage the cutting head. Also, when portions of the strip material are cut off during the laser and/or plasma cutting process, internal residual stresses can cause the strip material to deform and cause damage to the cutting head of the laser cutter and/or the plasma cutter. In addition, the quality of the cut will vary as the flatness of the material varies.
For optimum part production, a strip material should have uniform flatness along its cross-section and longitudinal length, and be free from any shape defects and any internal residual stresses. To prepare a strip material for use in production when the strip material is removed from a coil, the strip may be conditioned prior to subsequent processing (e.g., stamping, punching, plasma cutting, laser cutting, etc.). Levelers are well-known machines that can substantially flatten a strip material (e.g., eliminate shape defects and release the internal residual stresses) as the strip material is pulled from the coil roll. Levelers typically bend a strip material back and forth through a series of work rolls to reduce internal stresses by permanently changing the memory of the strip material.
Typically, the work rolls of a leveler are driven using a constant speed and rolling torque as a strip material is processed through the leveler. However, applying a constant torque and constant speed to the work rolls may only be effective to remove residual stresses near the surface of the strip material because only the surface of the material is stretched or elongated beyond the yield point of the strip material. This leaves unstretched portions in the thickness of the strip material resulting in relatively minor or negligible permanent change to internal stresses of the strip material.